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Alexandrite

Green in sunlight. Red in lamplight. Color-changing alexandrite is nature’s magic trick.

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Chrysoberyl Variety

Alexandrite is the color-change variety of the mineral chrysoberyl.

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Green by Day

Alexandrite is bluish green in daylight or fluorescent light.

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Red by Night

Alexandrite is purplish red in incandescent light or candlelight.

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Star-shaped Twin

This alexandrite specimen is made up of three interpenetrant crystals.

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Brazilian Gem

Brazil is one of the most important alexandrite sources.

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Re-entrant Angle

Notches marking the edge of each crystal are called re-entrant angles.

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Overview

About Alexandrite

About Alexandrite Gem
Often described by gem aficionados as “emerald by day, ruby by night,” alexandrite is the very rare color-change variety of the mineral chrysoberyl. Originally discovered in Russia’s Ural Mountains in the 1830s, it’s now found in Sri Lanka, East Africa, and Brazil, but fine material is exceptionally rare and valuable.

Alexandrite Description

Alexandrite History and Lore


Birthstones & Anniversaries

Alexandrite is a birthstone for June, along with pearl and moonstone. Alexandrite is also the gem for the 55th wedding anniversary.

1830

The year alexandrite was discovered in Russia’s Ural Mountains.


Czar Alexander II

Gem’s namesake who emancipated Russia’s serfs and was assassinated in 1881.


580nm

This absorption band allows alexandrite to shift from red to green when viewed under different light sources.


Facts

  • Mineral: Chrysoberyl
  • Chemistry: BeAl2O4
  • Color: Bluish green in daylight, purplish red in incandescent light
  • Refractive Index: 1.746 to 1.755
  • Birefringence: 0.008 to 0.010
  • Specific Gravity: 3.73
  • Mohs Hardness: 8.5

Treatments

There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.

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Synthetics

Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.

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Imitations

Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.

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gem love

Why We Love This Gemstone

1
Color Change

Making alexandrite change color from green to red is the world’s most fun use of a penlight.

2
Light Source

This gem provides dramatic proof of how much the light source affects color in gems.

3
Phenomena

Alexandrite can show both color change and a cat’s-eye: two phenomena in one gem.

Quality Factors

Color

quality factors

Fine alexandrite is green to bluish green in daylight and red to purplish red in incandescent light.

Clarity

quality factors

Good quality alexandrite has few inclusions. Rarely, needle-like inclusions create a cat’s-eye.

Cut

quality factors

Alexandrite is most often available in mixed cuts. Its rarity means it is often cut to save weight.

Carat Weight

quality factors

Most cut gems weigh less than one carat. Larger, higher-quality gems rise in price dramatically.

Alexandrite Quality Factors: The Comprehensive Guide

Research

Explore sources, gemological research, and the role of gems in history.

Alexandrite cabochon in fluorescent (left) and incandescent light (right).

Cat’s-Eye Alexandrite with Unique Inclusion Pattern

Makoto Miura and Yusuke Katsurada , Jan 26, 2018 Read Article

Titanium-Bearing Synthetic Alexandrite and Chrysoberyl

Jennifer Stone-Sundberg , Jan 31, 2014 Read Article
HOC synthetic alexandrite inclusion.

Challenges in Orienting Alexandrite: The Usambara and Other Optical Effects in Synthetic HOC-Grown Russian Alexandrite

Jennifer Stone-Sundberg , Apr 30, 2014 Read Article
Large Sri Lankan alexandrite

Fine Corundum, Paraíba Tourmaline, and Alexandrite – Tucson 2014

Duncan Pay , Apr 30, 2014 Read Article